This invention relates to the field of non-lethal impact munition, and more particularly to munition that are intended to fire a projectile at the body of a target to inflict blunt trauma and elicit pain compliance without causing serious bodily injury.
Several impact projectile designs for non-lethal munition are currently available that incorporate some type of compliant nose of the projectile to dissipate energy upon impact with the target. These projectiles are intended to be direct-fired at the target to deliver blunt trauma for pain compliance. For maximum projectile effectiveness, the pain inflicted by the projectile impact must be sufficient to force compliance, yet the delivered energy low enough to prevent serious bodily injury. Total projectile weight and weight distribution are important for projectile stability and effectiveness of the delivered energy. The projectile material of these commercially available designs are usually a low-density plastic or rubber to lessen the impact injury potential. Different methods have been used to increase the projectile weight, such as over-molding a rubber material on a metal slug, or simply using a denser material to mold the entire projectile. These methods do not allow the mass properties of the projectile to be precisely controlled, and in the case of a over-molded slug, can be difficult to manufacture repeatedly.
Operationally, the most important factor for non-lethal munition design is projectile accuracy, which is achieved through the structural design of the projectile as well as maximizing projectile velocity. The most challenging problem for developing an optimum non-lethal munition is to satisfy the competing requirements of maximum velocity, pain compliance, and minimal chance of serious bodily injury when directly fired at the target. The use of compliant noses for the projectile, such as a sponge or foam, dissipate energy upon impact with the target by compression of the foam or sponge by elastic deformation, and the energy required to further compress the sponge or foam increases as the material is compressed. An improved response can be achieved by using a rigid nose material which will crush under an impact load through plastic deformation. The energy required to compress a rigid nose is much higher initially and then drops off as the material fails and a crush zone is formed. The total energy required to deform the nose will depend on the material and its response to impact. To meet the non-lethal performance requirements, energy dissipation through deformation of the nose must be maximized.
Two parameters, namely, blunt trauma inflicted on the human target and the potential for penetration into the body must be considered when designing an impact projectile to be non-lethal. Most non-lethal projectiles have relatively low mass, and are fired at a low velocity, 300-500 feet per second, relative to lethal projectiles. Consequently, the energy transferred to the target is usually not sufficient to cause a serious blunt trauma injury, such as would result from rapid compression of the thoracic cavity during impact. Significant testing has been done to evaluate the parameters associated with blunt trauma injuries from projectile impacts using sophisticated models that simulate compression and deflection of the ribcage and thoracic region. This data has also been compared to injury potential using cadaver test specimens, providing some correlation to the response in the human body.
For the case of penetration, testing has also been done to characterize the energy per unit area required to penetrate the human body using simulated gelatin models, which has also been correlated against cadaver testing. Because the total energy of a non-lethal projectile is relatively low, the controlling parameter for penetration becomes the cross-sectional area of contact when the projectile impacts the target. For larger non-lethal munition, such as 37, 38 or 40 millimeter calibers, the cross-sectional area of impact is usually sufficient to prevent the penetration threshold from being reached, and penetration is highly unlikely. For the case of a 12 gauge projectile, controlling penetration is much more difficult. The small initial diameter can contribute to a fairly high energy per unit area, particularly when the projectile velocity is high to maximize accuracy at longer ranges. With these constraints, one of the only options for the designer is incorporate a feature into the project which expands the impact area through deformation of the projectile nose or body to sufficiently reduce the total energy per unit area to a level below the penetration threshold. Of course, practical considerations prevent some solutions to this problem, such as using a very compliant projectile nose that deforms to a larger surface area on impact. A very compliant nose will also deform as the projectile travels down the barrel of the launcher, engaging the rifling bands and causing damage to the nose material. This scenario will likely affect the spin of the projectile in the rifle bore, and decrease the stability of the projectile in flight.
With the increased use of non-lethal munition by law enforcement, corrections, and military personnel world-wide, there has been a constant need for more effective and higher performing products. The most requested improvements are increased range and increased accuracy, while maintaining the effectiveness of the product with respect to pain compliance and non-lethality. To achieve the optimum range in accuracy in a projectile, it is necessary to maximize the velocity within the constraints of delivered impact energy and penetration potential. As explained above, the diameter of the projectile is a critical factor in determining the lethality parameters. A 12 gauge projectile can exceed the penetration threshold even though the velocity and impact energy are not excessive. Any attempt to decrease the velocity to prevent penetration from occurring will have a negative effect on the range and accuracy of the projectile, as well as decreasing the effectiveness of the blunt impact. The best solution involves controlling the penetration potential by increasing the surface area upon impact, or by designing in a mechanism to dampen or dissipate energy on impact.
Another important parameter for long range non-lethal ammunition is the consistency of the velocity and impact energy over the operational range. This is particularly important when the ammunition is used with a launcher system that is designed to compensate for the range to the target by adjusting the projectile velocity, providing the maximum velocity at the maximum range, and decreasing the velocity proportionally as the range to the target decreases. With this type of system, the impact energy delivered to the target would be relatively constant over the operational range, and the weapons system could be used at short or long range with the same non-lethal performance. For this type of system to work, an inherent problem of non-lethal ammunition must be overcome, which is the wide velocity variance. Typical non-lethal 12 gauge ammunition is relatively light and is fired from shotgun shells using a loose smokeless powder charge. This configuration produces considerable variance in velocity due to the inconsistent burning of the propellant and the looser tolerances of the projectile in the shell.
Consequently, an improved non-lethal ammunition is necessary and the present invention addresses the problem of achieving optimal accuracy and range with a non-lethal impact projectile, while maintaining the critical non-lethal performance parameters. The invention also addresses the specific case of a non-lethal ammunition designed for a specific launcher system that adjusts the velocity of the projectile according to the range of the target, to maintain a relatively constant impact energy at the target independent of range.